Efficiency

    Cards (9)

    • Efficiency

      Measure of how much of the input energy is converted into useful output energy, rather than being wasted
    • Calculating efficiency

      1. In terms of energy: Efficiency = useful output energy transfer / total input energy transfer
      2. In terms of power: Efficiency = useful power output / total power input
    • To make energy transfers more efficient, we have to maximise the useful energy and minimise the wasted energy from a transfer
    • 100% efficiency is usually impossible
    • There is usually always some wasted heat energy in the form of heat / thermal energy
    • Sometimes the definition of 'useful' energy can change - e.g. some lights are designed to provide heat and light, so the heat energy is also useful
    • Efficiency

      Useful output energy transfer / total input energy transfer
    • Power

      Measured in watts, W
    • We can increase efficiency in several ways: thermal insulation, lubrication and streamlining
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